The present invention relates to security fibers, a process for the preparation thereof and a security paper containing same.
Security documents such as bank notes, stocks, bonds, checks, warrants and identification cards need to be guarded by antifalsification measures and they are often made from a security paper having a security element in the form of fibers, strips or threads embedded therein.
Japanese Laid-open Patent Application No. 90-293500 discloses a security paper containing security fibers prepared by dyeing a natural or synthetic fiber uniformly with a visible or invisible fluorescent dye and cutting the dyed fiber to a given length. However, such monochromatic security fibers have limited effectiveness in the prevention of counterfeiting.
Korean Patent No. 111,723 describes multi-colored security fibers prepared by a process comprising the steps of: placing a mask over a section of a fiber and dyeing the exposed section of the fiber with a first dye; replacing the mask over to the dyed section thereby exposing the undyed section; dyeing the undyed section of the fiber with a second dye; and cutting the fiber to a suitable length to obtain multi-colored security fibers having an enhanced security feature.
However, this complicated process has a low productivity.
Accordingly, it is a primary object of the present invention to provide an improved process for preparing security fibers suitable for use in a security paper.
It is another object of the present invention to provide novel security fibers suitable for use in a security paper.
It is still another object of the present invention to provide a security paper containing security fibers having an enhanced security features.
In accordance with one aspect of the present invention, there is provided a process for preparing security fibers which comprises the steps of: i) braiding 5 to 30 denier fibers to form a twine; ii) dyeing the twine with a dye or pigment; iii) drying the dyed twine; and iv) cutting the dried twine to give the security fibers in the form of cut fibers.